In general, as coated tools, there are inserts which are detachably attached to the tip portion of an insert holder used for turning or plaining of a work material, such as various types of steels and cast iron, drills used for drilling or the like of the work material, and solid type end mills used for facing, grooving, shoulder milling, and the like of the work material. In addition, as coated tools, indexable end mills and the like are also known which include inserts detachably attached thereto and perform cutting in the same manner as the solid type end mills.
For example, as described in PTL 1, as a coated tool, a coated tool is known in which a hard coating layer including a layer made of complex nitride of Al, Cr, and B (hereinafter, referred to as (Al, Cr, B)N) is vapor-deposited on the surface of a body (hereinafter, referred to as a tool body) made of tungsten carbide (hereinafter, referred to as WC)-based cemented carbide. Regarding the conventional coated tool, it is known that the (Al, Cr, B)N layer forming the hard coating layer is excellent in adhesion, high-temperature oxidation resistance, and wear resistance and thus exhibits excellent cutting performance.
In addition, regarding the conventional coated tool, it is known that coatings are formed by an ion plating method or a sputtering method. For example, regarding the coating formation using arc ion plating, a method using an arc ion plating apparatus 100 as shown in FIGS. 1A and 1B is known. The arc ion plating apparatus 100 includes: a rotating table 101 on which tool bodies (cemented carbide bodies) 1 are placed; a heater 102 for heating the tool bodies 1, a reaction gas inlet 103 for introducing a reaction gas; a gas outlet 104 for discharging the gas to the outside of the system; two anode electrodes 111 and 112; and two cathode electrodes 113 and 114. The anode electrode 111 and the cathode electrode 113 are connected to an arc power supply 115 provided outside the apparatus 100, the anode electrode 112 and the cathode electrode 114 are connected to an arc power supply 116 provided outside the apparatus 100, and the rotating table 101 is connected to a bias power supply 117 provided outside the apparatus 100. The tool bodies (cemented carbide bodies) 1 are mounted on the rotating table 101 in the arc ion plating apparatus 100, the tool bodies 1 are heated to a temperature of 500° C. by the heater 102, nitrogen gas as the reaction gas is introduced into the apparatus 100 through the reaction gas inlet 103 to form a reaction atmosphere at 2 Pa, and a bias voltage of −100 V is applied to the tool bodies 1 from the bias power supply 117. It is also known that under such conditions, a current of 90 A is supplied by the arc power supply 115 to between the anode electrode 111 and the cathode electrode 113 in which an Al—Cr—B alloy (Al—Cr—B alloy target) with a predetermined composition is set, so as to generate arc discharge such that the (Al, Cr, B)N is vapor-deposited on the surface of the tool bodies 1 and thus a coated tool can be produced.
In addition, as described in PTL 2, as a coated tool, a coated tool is known in which a hard coating layer including a layer made of complex nitride of Al, Cr, and Si is vapor-deposited on the surface of a body (hereinafter, referred to as a tool body) made of tungsten carbide (hereinafter, referred to as WC)-based cemented carbide. Regarding the conventional coated tool, it is known that the layer made of complex nitride of Al, Cr, and Si forming the hard coating layer is excellent in adhesion, high-temperature oxidation resistance, and wear resistance and thus exhibits excellent cutting performance.
In addition, regarding the conventional coated tool, it is known that coatings are formed by an ion plating method or a sputtering method. For example, regarding the coating formation using arc ion plating, a method using an arc ion plating apparatus 200 as shown in FIGS. 4A and 4B is known. The arc ion plating apparatus 200 includes: a rotating table 201 on which tool bodies (cemented carbide bodies) 2 are placed; a heater 202 for heating the tool bodies 2; a reaction gas inlet 203 for introducing a reaction gas, a gas outlet 204 for discharging the gas to the outside of the system; two anode electrodes 211 and 212; and two cathode electrodes 213 and 214. The anode electrode 211 and the cathode electrode 213 are connected to an arc power supply 215 provided outside the apparatus 200, the anode electrode 212 and the cathode electrode 214 are connected to an arc power supply 216 provided outside the apparatus 200, and the rotating table 201 is connected to a bias power supply 217 provided outside the apparatus 200. The tool bodies (cemented carbide bodies) 2 are mounted on the rotating table 201 in the arc ion plating apparatus 200, the tool bodies 2 are heated to a temperature of 500° C. by the heater 202, nitrogen gas as the reaction gas is introduced into the apparatus 200 through the reaction gas inlet 203 to form a reaction atmosphere at 2 Pa, and a bias voltage of −100 V is applied to the tool bodies 2 from the bias power supply 217. It is also known that under such conditions, a current of 90 A is supplied by the arc power supply 215 to between anode electrode 211 and the cathode electrode 213 in which an Al—Cr—Si alloy (Al—Cr—Si alloy target) with a predetermined composition is set, so as to generate arc discharge such that the complex nitride of Al, Cr, and Si is vapor-deposited on the surface of the tool bodies 2 and thus a coated tool can be produced.
However, regarding the coated tool, in order to further improve cutting performance, particularly chipping resistance, wear resistance, and the like, various suggestions on the structure of the hard coating layer have been made.
For example, in PTL 3, as a coated tool improved in fracturing resistance by suppressing the fracturing of the coating layer on the rake face, and also improved in wear resistance of the flank face, the following coated tool (end mill) is described. That is, a coated tool (end mill) is described in which the coating layer is formed of columnar crystal grains, the thickness of the coating layer on the rake face is smaller than that on the flank face, the coating layer is formed of two layer regions including a lower layer region formed on the coating layer body side and an upper layer region which has a greater average grain width than that of the lower layer region and is formed on the surface side of the coating layer, the ratio of the thickness of the upper layer region to the thickness of the coating layer on the rake face is less than the ratio of the thickness of the upper layer region to the thickness of the coating layer on the flank face, and the average grain width of the columnar crystal grains on the rake face is smaller than the average grain width of the columnar crystal grains on the flank face.
In addition, for example, in PTL 4, as a coated tool with a coating compatibly satisfying wear resistance and toughness and having excellent adhesion to a base material, the following coated tool is described. That is, a coated tool is described in which the coating formed on the base material includes a first coating layer, the first coating layer includes a fine structure region and a coarse structure region, the compound forming the fine structure region has an average grain size of 10 nm to 200 nm, the fine structure region exists in a range from the surface side of the first coating layer to a thickness of 50% or greater with respect to the thickness of the entire first coating layer, and has an average compressive stress in a range of −4 GPa to −2 GPa, the first coating layer has a stress distribution in the thickness direction thereof, and has two or more maximum or minimum values in the stress distribution, and the maximum or minimum values located closer to the surface side in the thickness direction have higher compressive stress.